1. Field of the Invention
This invention relates generally to a drywall finishing apparatus and particularly relates to a simple, lightweight device which applies wallboard compound and wallboard tape to a wallboard joint while wiping the tape and compound, all during the same operative stroke.
2. Description of Prior Developments
Drywall, sheetrock or wallboard is typically fastened to the internal framework of most residential and commercial buildings. Large panels of wallboard are usually nailed to wooden "studs" to form the interior wall and ceiling surfaces. In order to provide a smooth, continuous surface across the cracks or joints formed between abutting wallboard panels, thin covering strip of a fiberous or paper-like material is applied so as to cover the crack.
Although this covering material lacks any adhesive coating, it is referred to in the trade as wallboard "tape". In order to permanently secure this tape across the wallboard joints, an adhesive called wallboard compound or "mud" is first spread over the wall and the tape is subsequently applied to the joint. This procedure has typically required considerable effort and skill. In order to expedite this tape application procedure, various devices have been developed which simultaneously apply the tape and compound over the joint.
While these applicators generally apply tape and compound at a faster rate than that possible by manual methods using simple hand tools, they have been found to perform less than totally satisfactorily. That is, most conventional mechanized tape and compound applicators experience one or more of a host of annoying drawbacks well known to be associated with such applicators. This has resulted in generally poor acceptance of these devices by the building trades.
A particularly bothersome drawback of several conventional compound and tape applicators is the need to wipe down the tape and compound once it has been applied to the joint. That is, these applicators are unable to adequately smooth or iron out the tape and compound so as to form a continuous, even surface during the same stroke in which they are dispensed. This condition requires an additional follow-up or clean-up procedure wherein excess compound is removed with a putty knife and irregularities such as bumps and bubbles formed beneath the tape are flattened. In practice, this type of operation requires at least two workmen - one to operate the applicator and one to follow behind to clean up the excess compound and smooth out any surface imperfections.
The irregularities referred to above are often the result of an intermittent or poorly controlled wallboard compound feed rate. Several devices are fed by a spring-loaded mechanism similar to those used in grease guns. These spring-loaded feed mechanisms frequently fail to provide a smooth, continuous supply of compound to the applicator nozzle. This results in a sporadic flow of compound to the tape and generates bubbles within the compound which appear as bumps or depressions beneath the tape.
Another drawback associated with presently available automated or mechanized tape and compound applicators is their cumbersome and complicated structure. An applicator loaded with compound can weigh up to 40 pounds and extend over a length of 4 to 5 feet. Use of such a device rapidly fatigues the operator. Moreover, fine finishing work is most difficult to achieve with such an awkward, heavy device.
The complicated structure of many applicators leads to frequent breakdowns and necessitates involved and costly repairs. One such applicator is known to include over 20 moving parts and is highly prone to failure.
Still another drawback of prior applicators is their inability to adequately produce a clean, "tight" corner or angle joint. That is, while somewhat satisfactory results have been achieved in applying tape and compound on flat surfaces, angle joints formed along corners and at the junction of walls and ceilings have continually presented an unsolved problem to conventional applicators. These applicators are simply unable to apply the tape and compound at the 90 degree angle typically formed at corners and at wall-ceiling joints.
Accordingly, a need exists for a simple, lightweight applicator which smoothly and efficiently applies a continuous even coating of wallboard compound to a strip of wallboard tape and simultaneously wipes down the tape so as to obviate the need for a subsequent wiping and clean-up procedure.
The realization of these and various other objects, features and attendant advantages of the present invention will be more fully appreciated from the following description when considered in connection with the accompanying drawings, in which the same reference numbers designate the same or corresponding parts throughout.